I\'m right in the middle of TWO Ulthwe army boxes. If you want them not quite so black as DR\'s technique you could prime white (yes white) or gray, then a couple heavy washes of an acrylic medium (Future floor finish mix) with a little black paint and black ink. It will tint the surfaces nicely and sink into the crevices. You\'ll end up with troops that look black, but still have some contrast without sucking all the light out of the room. You can go back later if you want and touch up and highlight.
For the bone, basecoat graveyard earth, then highlight khaki and then highlight bleached bone. (or drybrush khaki, then lighter drybrush of bleached bone)
For fast gems, paint a light base coat (blood red or what not) then glaze (or very selectively wash) with dark brown/black, concentrating on the upper part of the gem a little more. Add a dot of white for a specular reflection at the top, and optionally wash with the same color ink as the gem after that. Just pick a few gems to paint, since gem vs. bump on Eldar armor seems random, for the most part.